Requests for safety in resin binders for toner have been stronger in recent years. In addition, an odor emitted when the resin binders are exposed to an environment at high temperature during the melt-kneading in toner manufacturing or during fusing and fixing in using tones is a problem to be solved. In view of this, therefore, various methods have been studied for reducing the amount of monomers remaining in the resin binder.
For example, there is a method in which polymerization initiators having different half lives are used (JP-A-Hei-7-120971 and JP-A-Hei-7-49588). In these methods, however, the effect of reducing the styrene content is insufficient, and increase in the reaction time, variation in the molecular weight distribution of the resin, difficulty in adjusting various physical properties, and the like are caused. Moreover, odor due to remnants of the initiator is a matter to be concerned.
Also, there has been proposed a method for reducing the amount of remaining monomers by distilling water in the reaction system off as water vapor after polymerizing monomers in a suspension polymerization system (JP-A-Hei-8-328311).
A method in which an alkali metal hydroxide is added (alkaline treatment) has been also proposed (JP-A-Showa-61-176603). However, since care must be taken to avoid hydrolysis, as noted therein, this method cannot be used in a wide variety of applications. In cases that hydrolysis is not caused, the alkali metal hydroxide is to remain in the resin, so that influence on the physical properties of the toner is a matter to be concerned.
Further, there has been proposed a method of improving manufacturing facilities for toners (JP2000-298374 A). In this method, the effect of reducing the styrene content is insufficient, and introduction of additional equipment is required.